1. Technical Field
The present invention relates to a surface acoustic wave element and a surface acoustic wave device using the same.
2. Related Art
A surface acoustic wave device (hereinafter referred to as a “SAW device”) is widely used in applications for compact information equipments such as HDDs (Hard Disk Drives), mobile computers, or IC cards, or mobile communication equipments such as cellar telephones, automobile telephones, or paging systems.
FIG. 6 is a schematic perspective view of an existing SAW device 1, in which a piezoelectric element 4 is contained in a package.
An IDT (Inter Digital Transducer) composed of a pair of comb-like electrodes 5a, 5b is formed around a center of the piezoelectric element 4, and reflectors 6, 6 are formed at opposite sides of the IDT 5, respectively.
The piezoelectric element 4 is bonded to an inner bottom of the package 2 using an adhesive 3 in a manner to bond a central area of the piezoelectric element 4 to the package 2 by the adhere in order to prevent the piezoelectric element 4 from swinging significantly enough to clash with the package 2 at the time of, for example, a drop of an electronic device such as a cellar phone or the like equipped with the SAW device.
The piezoelectric element 4 has a pair of terminals 7, 7 electrically connected to the comb-like electrodes 5a, 5a, respectively, in which the terminals 7, 7 are connected to electrodes at a side of the package 2 or to a semiconductor element 8 by wire bonding. Herein, the pair of terminals 7, 7 are disposed on the adhesive 3, i.e., at the central area of the piezoelectric element 4 since the adhere 3 is used as a receiver for weight which is applied at the time of the wire bonding to the terminals 7, 7.
In the SAW device 1 having the central area of the aforementioned piezoelectric element 4 bonded to the package 2, however, there is a fear of a change in an oscillation property due to warpage in the area formed with the IDT 5, which is resulted from contraction stress of the adhesive 3 or the like.
FIG. 7 is a schematic perspective view of a SAW device 9 which has been contemplated to reduce influence on an oscillation property, which is given by the contraction stress of the adhesive 3 as described above.
In other words, in the case where the SAW device 9 is contained in the electric device which is hardly moved, the piezoelectric element 4 is less likely to clash with the package 3, so that peripheral area other than the area formed with the IDT 5 is to be bonded to the package 2 by the adhesive 3. As described above, the terminals 7, 7 are disposed at the same peripheral area where the adhesive 3 is disposed since the adhesive 3 is used as a receiver for a weight at the time of the wire bonding (see, e.g., JP-A-2002-26656).
JA-A-2002-26656 is an example of related art.
In consideration of both cases where the SAW device is used in applications for mobile electronic devices such as a cellar telephone and used in applications for hardly mobile electronic devices, it is necessary to prepare two types of SAW devices 1, 9 different in positions of the terminals 7, 7, resulting in relatively expensive design development costs as well as causing increase in a stock amount.